Irreducible representatives of standard-form arrows #
The standard-form AR quiver indexes parallel arrows by the numerical arrow-multiplicity entry. Here that finite index is identified with the literal occurrences of the required label in the chosen right almost-split middle term. The corresponding middle-term components give concrete irreducible module morphisms. Pulling this assignment to the based universal cover supplies the initial arrow representatives for the two-sided Bongartz--Gabriel normalization.
Occurrences of y in the chosen right almost-split middle term ending at
x.
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The number of literal occurrences with endpoints (y,x) is the official
standard-form arrow multiplicity.
Abstract standard-form arrows are canonically chosen representatives of the corresponding literal middle-term occurrences.
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Forgetting the retained label identifies the disjoint union of all occurrence fibres with the full finite middle-index type.
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The displayed middle indices at x are exactly the standard-form arrows
leaving x, with the target label retained in the dependent sum.
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The irreducible module morphism represented by one reversed standard-form arrow.
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The arrow attached to the i-th middle index is its actual chosen
right-mesh component.
The terminal map of the chosen right mesh, after identifying its endpoint with the selected indecomposable representative.
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The chosen standard-form right sink is right almost split.
The chosen standard-form right sink is right minimal.
Take the occurrence component of an arbitrary replacement sink at one standard-form vertex.
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The initial arrow representative is the occurrence component of the chosen right almost-split sink.
Every chosen standard-form arrow representative is irreducible.
A nonprojective standard-form vertex as the corresponding nonzero right boundary of the finite tau-category.
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The finite-tau positive translate and the standard-form translation have the same underlying label.
The first map of the chosen right mesh, with its source identified with the standard-form translate.
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The first map of the chosen nonprojective standard-form right mesh is monic: it is the selected Auslander--Reiten kernel inclusion, up to the two displayed source identifications.
The identified first map of a chosen nonprojective right mesh is left almost split.
The identified first map of a chosen nonprojective right mesh is left minimal.
The identified chosen right-mesh source and sink have zero composite.
The identified chosen right-mesh source and sink have zero composite.
The identified first map of a chosen nonprojective right mesh is a weak kernel of its identified sink. Thus every morphism killed by the sink factors through the standard-form translate.
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The finite middle index at a cover vertex, regarded as its corresponding outgoing arrow downstairs.
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The target cover vertex obtained by lifting one displayed middle
occurrence from W.
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The unique lifted outgoing arrow represented by one displayed middle occurrence.
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The displayed middle indices exhaust the outgoing star at every universal-cover vertex.
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The abstract star-equivalence lift is the explicit arrow obtained by
extendOld.
The downstairs module object attached to a universal-cover vertex.
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An arbitrary choice of module representative for every reversed arrow of the based universal cover.
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The polarized partner of the lifted arrow represented by one displayed middle occurrence at a nonprojective cover vertex.
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Assemble the representatives on the polarized partner arrows into the
source map of the lifted mesh at W.
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Projection to the i-th displayed summand recovers the representative
on its polarized partner arrow.
Projection to the i-th displayed summand recovers the representative
on its polarized partner arrow.
Reassemble all arrow representatives leaving W into a single map from
the chosen right-mesh middle term to its endpoint.
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The i-th component of the reassembled sink is the representative on
the corresponding lifted arrow.
The i-th component of the reassembled sink is the representative on
the corresponding lifted arrow.
Initial irreducible arrow representatives on the universal cover, pulled back from the chosen standard-form occurrence representatives.
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Every initial universal-cover arrow representative is irreducible.
Reassembling the initial lifted representatives recovers the chosen downstairs right almost-split sink exactly.
Occurrence component of a replacement right sink at one universal-cover vertex.
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On an explicitly indexed lifted arrow, sink-component extraction is literally precomposition with the corresponding middle inclusion.
Extracting a displayed middle component from the sink reassembled from
D returns that arrow representative.
Reassembly followed by component extraction is the identity for every universal-cover arrow, not only for the explicitly displayed lift.
Initially, every lifted arrow is the occurrence component of the chosen downstairs right almost-split sink.
Replace all arrow representatives whose reversed-quiver source is one fixed universal-cover vertex.
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Reassembling at the replaced vertex recovers the replacement sink exactly.
A replacement at W leaves every realized sink at a different source
vertex unchanged.
The inductive invariant: every realized sink is minimal right almost split.
- rightAlmostSplit (W : MeshCategory.RightMeshData.UniversalCover.Vertex S.standardFormRightMeshData x₀) : QuotientSubmoduleEquidistribution.IsRightAlmostSplit (S.standardFormUniversalRealizedSink x₀ (fun {W Z : MeshCategory.RightMeshData.UniversalCover.Vertex S.standardFormRightMeshData x₀} => D) W)
- rightMinimal (W : MeshCategory.RightMeshData.UniversalCover.Vertex S.standardFormRightMeshData x₀) : QuotientSubmoduleEquidistribution.IsRightMinimal (S.standardFormUniversalRealizedSink x₀ (fun {W Z : MeshCategory.RightMeshData.UniversalCover.Vertex S.standardFormRightMeshData x₀} => D) W)
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The initial occurrence-component assignment satisfies the sink condition.
Replacing one realized sink by another minimal right almost-split sink preserves the inductive invariant globally.
Simultaneously replace the outgoing representatives at every cover vertex of one Bongartz--Gabriel height. No enumeration of the (potentially infinite) height fibre is required because each arrow has a unique source.
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At a selected height, reassembling the simultaneous replacement returns the supplied sink at that vertex.
Outside the selected height, simultaneous replacement leaves the realized sink unchanged.
A simultaneous height replacement by minimal right almost-split sinks preserves the global sink condition.